Contraction joint



Nov. 14, 1933. J. N. HELTZEL 1,935,028

CONTRACTION JOINT Filed May 7. 1927 Patented Nov. 14, 1933 1,935,028 I -CdNTRQACTIQN-JOINT. M ,7

Jthn N. ileuzer-warrem-bmbfi Application May 7,: 1927. 7 Serial No. 189,543 4,ciaimsgj" o1.;s 17) which are embedded time concrete .to define- The present invention relates to contraction joints for-concrete roads and pavements; and aims to provide novel means for producing and controlling the breaking of the concrete along a straight or predetermined line in a I'nann'er'to have the advantages of a natural break without thedisadvantage of the irregularline'of a natural break.

It has been the practice in building concrete roads and pavements to permit.- the transverse contraction cracks to developnaturally, as the concrete dries out andthe same contracts. i This has the advantage of causing irregular interlocking surfaces on the sections or slabs, with protruding stones, pebbles or gravel entering recesses in the confronting surfaces of the adjacent slabs, so as to prevent relative vertical displacement of the slabs. The natural breaks have the disadvantage, however, of occurringat irregular points along the road and extending along irregular lines across the road.

The present invention. aims .to provide means for controlling the breaks along definite lines at the surface of the concrete, with the slabsinterlocked between the surface and'sub-bas'e similar to that which occurs with a natural break,

in order that the break at the surface .of the concrete will extend along a straight or regular line, whereas the break below the surface will be irregular, similar to a natural break. The breaking of the concrete is thus controlled to provide slabs of predetermined proportions,'with a neat appearance of the breaks at the surfaceof the concrete, and the adjacent surfaces of the slabs interengaged to .prevent relative vertical displacement thereof. a I

With the foregoing and other objects in view, which will be apparent as theinvention is more fully understood, the invention resides in the construction and arrangement of parts as hereinafter described and claimed, it being under-- Fig. 3 is a fragmentary perspective view illus-' trating a modification.

In carrying out the invention there are provided division strips '7, as seen in Figs. 1 and 2,

of sheet metal, fibre, or other suitable. material,

thelines of breaks thereof. As shown; "the strips are employed forbotli the longitudinal and trans verse breaks or joints, although they are "especially intended for thetransverse' contraction joints. The strips"! 'are I of alwid'th to: extend from thesurface of the concrete part Way down,

with their lower edges spaced abovethe subbase,-so 'that the division stripsor plates do not divide the concrete'completely.

The strips 7haveportions or pockets '8 presse to opposite sides and forming protuberances with recesses or cavities at the-opposite sides. portions 8 :are 5 preferably of irregular form. and arrangement, and are of pyramidal or similar shape, to represent orsimulate broken stone, such as used as aggregate in road construction. Each portion 8 has a'naperture 9 at its apex, to permit the air to escape from the cavities, so as to avoid air pockets or voids in the concrete, inasmuch as the material, while plastic, may

readily flow into the cavities without the air being trapped therein.

gage acrossthe lower edges of blades or mandrels used to force the strips down into the plastic material, and a machine may be used for installing the strips or plates 7 according to the method and machine disclosed in my applications Serial Nos. 3,972 and 6,806'filed January 22, 1925 and February 4, 1925, respectively. The bent back portions 10 also anchor the strips in the concrete.

Each strip or plate '7 has a rib-11 pressed toward one side immediately below the upper edge of the strip, in order to stiffen and reinforcethe strip and thereby provide a straight or regular line at the upper edge of the strip along the surface of the concrete.

By forcing the strips or plates 7 down into the These 7 concrete while it is still plastic, thestrips are embedded in the concrete, thereby dividing the concrete from its upper surface downwardly to a depth equal to the width of the-strips. Previous to installing the strips it is preferable that the stones or other coarse aggregate be forced down so as not to obstruct the depositing of the strips '7 in the concrete. This, with the use of j plain or smooth strips, results in losing the advantages of a natural break between the upper and lower edges of the strips, and the stone, rock or othercoarser aggregate do not lockthe slabs together against relative verticaland horizontal displacement. With the present strips,

however, the concrete entering the cavities formed by the portions 8 will provide for the interengaging of the slabs resembling a natural break, and the concrete will develop a natural break below the strips '7 so as to have a substantially natural break from its upper surface to the sub-base.

The portions 8 may be of triangular, square 7 and other polygonal" forms, andmay be" of. varioussizes', to resemble crushed stone or rock, and the apertures 9 may be punched in the strips or sheets 8, or maybe formed therein by punching or tearing when pressing the portions 8 i112.

the strips;

As shown in Fig. 3 the pressed portions 8 of the strip '7 are of circular and irregular curved shapes, so as to resemble pebbles or round stones,

each portion 8 having an aperture"- 9 atits apex. With this form of strip the adjacent surfaces of the slabs will be formed to imitate a s der the longitudinal strips 'Z,v said rods having lugs thereon or being otherwise deformed so as to be anchoredin the slabs. Longitudinal dowelsv 114 are embedded in the slabs l2 and extend un-- der: the transverse strips 'Lfor-holding the slabs in alinement, said dowels being smooth and pref erably treated so as to be free to slide in the slabs when the slabs contract and expand. The rods 13 and 14 may be embedded in the concrete during the pouring thereof, and the strips 7 may be deposited in the concrete subsequently over said rods.

Having thus described the invention, what is claimed as new is:' r

1. A division. strip to be embedded in concrete having a rib pressed therefrom immediately below its upper edge and having its lower edge bent back and extending upwardly to form an elongated open hook, said strip having pockets pressed therefrom, said pockets being distributed throughv out the length of the strip between said rib and hook.

2*. A divi'sion'strip adapted to be embedded in concrete having pockets pressed therefrom to receive the plastic concrete, said pockets having air outlet apertures at the' apices thereof;

3, A division strip adapted tobe: embedded; in

concrete having pockets pressed therefrom to JOEN N. HELTZEL. 

